1. Field of the Invention
The present invention generally relates to a method and apparatus for securing data contents stored in a non-volatile memory. More specifically, the present invention relates to a method and apparatus for preventing the unauthorized alteration, revision, or access of data contents stored in a flash memory by way of address and data scrambling such that unrecovered data are useless.
2. Description of the Related Art
As shown in FIG. 1, a micro controller unit (MCU) is a key component in a computer structure, which includes a flash memory 10 for storing executable programs. The current encryption and decryption systems do not offer any protection for data contents stored in the flash memory 10. Therefore, a person familiar with encryption and decryption techniques can easily read and access data stored in the flash memory 10. For instance, an executable program containing information such as a user""s password or identification can easily be accessed and published when stored in the flash memory 10. In addition, a person using special software (e.g., SOFT IN CIRCUIT EMULATOR or SOFT ICE) can easily alter a computer program as to access information stored in the flash memory 10 without having to know a user""s password, thereby stealing information and breaching security.
As an example, cellular phone companies generally incorporate important confidential and proprietary data regarding functions and capabilities of various cellular phones into executable programs using DSP. However, these important data cannot be safely protected against unauthorized access when stored in the flash memory. Accordingly, the flash memory is no doubt a serious security risk with respect to the protection of important data.
One way to solve the above-discussed problems is illustrated in FIG. 2, which combines an MCU and flash memory into an integrated circuit (IC) 20. In this way, the flash memory can only be accessed internally through a build-in data bus as to prevent decoding and unauthorized access and revision. However, this is not an ideal way to solve the above-discussed problems because manufacturing costs are significantly increased due in part to the fact that the flash memory and MCU are manufactured by different processes.
As such, the present invention takes advantage of the fact that reading and writing of the flash memory generally occurs during program loading or machine boot-up, which occurs infrequently. Therefore, through minimal logic and special designs, the present invention is able to protect the contents of data stored in the flash memory.
As previously described, the purpose of this invention is to provide a method and apparatus for securing data contents stored in a non-volatile memory. In particular, the executable programs are sized and processed as block based data, and through scrambling and random accessing, the order and position of the data contents are changed and a new combination is formed. Since the original data contents cannot be recovered without reversing the original process, the data contents in a flash memory are protected without incurring high manufacturing costs.